onloadはちょっとわかりませんが他はこう書けばOKです


function onEnterFrame(e:Event)
{
MovieClip(root).y = (this.usagi_mc.y - 50) * (-1);
MovieClip(root).x = (this.usagi_mc.x - 215) * (-1);
}

stage.addEventListener(Event.ENTER_FRAME, onEnterFrame);